Sex Differences in Sentiment-Scored Vocabulary Patterns in VAERS Free-Text Narratives of Four Major Vaccine Categories

Kae Matsumura; Megumi Horibe; Yoko Ino; Kana Sugishita; Tomofumi Yamazaki; Moe Maeno; Koichi Kageyama; Seiichiro Ito; Mugita Sato; Mahiro Chikahisa; Mayumi Kitamura; Mari Iwata; Kazuhiro Iguchi; Mitsuhiro Nakamura

doi:10.1248/bpb.b26-00304

Regular Article

Sex Differences in Sentiment-Scored Vocabulary Patterns in VAERS Free-Text Narratives of Four Major Vaccine Categories

Kae Matsumura, Megumi Horibe, Yoko Ino, Kana Sugishita, Tomofumi Yamazaki, Moe Maeno, Koichi Kageyama, Seiichiro Ito, Mugita Sato, Mahiro Chikahisa, Mayumi Kitamura, Mari Iwata, Kazuhiro Iguchi, Mitsuhiro Nakamura

Author information

Kae Matsumura
Laboratory of Drug Informatics, Gifu Pharmaceutical University, 1–25–4 Daigaku-Nishi, Gifu 501–1196, Japan
Megumi Horibe
Department of Nursing, School of Health Sciences, Asahi University, Gifu 501–0296, Japan
Yoko Ino
Laboratory of Pharmaceutical Health Care and Promotion, Gifu Pharmaceutical University, 1–25–4 Daigaku-Nishi, Gifu 501–1196, Japan
Kana Sugishita
Laboratory of Drug Informatics, Gifu Pharmaceutical University, 1–25–4 Daigaku-Nishi, Gifu 501–1196, Japan
Tomofumi Yamazaki
Laboratory of Drug Informatics, Gifu Pharmaceutical University, 1–25–4 Daigaku-Nishi, Gifu 501–1196, Japan
Moe Maeno
Laboratory of Drug Informatics, Gifu Pharmaceutical University, 1–25–4 Daigaku-Nishi, Gifu 501–1196, Japan
Department of Pharmacy, University of Miyazaki Hospital, 5200 Kihara, Kiyotake-cho, Miyazaki 889–1692, Japan
Koichi Kageyama
Laboratory of Drug Informatics, Gifu Pharmaceutical University, 1–25–4 Daigaku-Nishi, Gifu 501–1196, Japan
Seiichiro Ito
Laboratory of Drug Informatics, Gifu Pharmaceutical University, 1–25–4 Daigaku-Nishi, Gifu 501–1196, Japan
Mugita Sato
Laboratory of Drug Informatics, Gifu Pharmaceutical University, 1–25–4 Daigaku-Nishi, Gifu 501–1196, Japan
Mahiro Chikahisa
Laboratory of Drug Informatics, Gifu Pharmaceutical University, 1–25–4 Daigaku-Nishi, Gifu 501–1196, Japan
Mayumi Kitamura
Department of Nursing, School of Health Sciences, Asahi University, Gifu 501–0296, Japan
Mari Iwata
Yanaizu Pharmacy, Gifu 501–6103, Japan
Kazuhiro Iguchi
Laboratory of Community Pharmacy, Gifu Pharmaceutical University, 1–25–4 Daigaku-Nishi, Gifu 501–1196, Japan
Mitsuhiro Nakamura Corresponding author
Laboratory of Drug Informatics, Gifu Pharmaceutical University, 1–25–4 Daigaku-Nishi, Gifu 501–1196, Japan

Keywords: Vaccine Adverse Event Reporting System, sentiment analysis, text mining, vaccine, sex difference, pharmacovigilance

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Supplementary material

2026 Volume 49 Issue 9 Pages 1561-1569

DOI https://doi.org/10.1248/bpb.b26-00304

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Abstract

Free-text narratives in vaccine adverse event reports contain symptom descriptions and contextual wording that can be characterized using text mining. However, lexicon-based sentiment scores in medical narratives should be interpreted as vocabulary patterns rather than direct measures of patients’ emotional states. We evaluated sex-specific and vaccine-specific patterns in sentiment-scored and emotion-category assignment vocabulary in Vaccine Adverse Event Reporting System (VAERS) narratives for coronavirus disease 2019 (COVID-19), influenza, human papillomavirus (HPV), and measles–mumps–rubella (MMR) vaccines. Public VAERS reports received from 2010 to 2024 were analyzed. VAERSDATA, VAERSVAX, and VAERSSYMPTOMS were linked by VAERS_ID, with duplicate records removed. Report-level AFINN scores were normalized per 100 words. Sensitivity analyses excluded common clinical and symptom-related terms. Effect sizes, 95% confidence intervals, adjusted linear regression models with HC3 robust standard errors, and NRC emotion-category assignment profiles were evaluated. After duplicate handling, 1022460 COVID-19, 148489 influenza, 41212 HPV, and 47459 MMR reports were analyzed. Female-associated reports generally showed slightly lower primary AFINN scores than male-associated reports, although effect sizes were negligible. Excluding clinical and symptom-related terms attenuated or reversed these differences. Adjusted regression models showed only small associations between sex and AFINN scores. NRC analyses demonstrated clearer vaccine-specific than sex-specific vocabulary patterns. VAERS narratives showed only small sex-related differences but distinct vaccine-specific patterns in sentiment-scored and emotion-category assignment vocabulary. These findings should be interpreted as lexicon-derived vocabulary patterns rather than direct measures of psychological responses, vaccine perceptions, or clinical outcomes.

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